Sawtooth & Western Smoky Mtns

Avalanche problems

• 

  Persistent Slabs

  N

  NE

  E

  SE

  S

  SW

  W

  NW

  • Alpine
  • Treeline
  • Below treeline

  Likelihood

  Very Likely

  Size

  2.5–3.5

  What and where is it? Dense, 2-5 foot thick slabs exist on most slopes. The weak layers (crusts and weak, sugary faceted snow) are most suspect on W-NW-N-NE-E-SE facing slopes at middle and upper elevations (near and above ~8500' in this zone), but more recently buried rain and sun crusts exist on most middle and upper elevation slopes.

  How can you recognize it? Assume the slab + weak layer setup exists on all slopes. Now is not the time to try to outsmart the snowpack. Expect to experience obvious signs of instability—snowpack collapsing and cracks shooting out from your skis or sled—in many areas.  

  How can you manage it? Sadly, today's answer is "stay off of, away from, and out from beneath all steep slopes." This zone received 5-7" of water (50-70" of dense snowfall) in the past week; there is little to no margin for error today. Natural avalanches are possible, and slides can be triggered remotely—from flat terrain below, above, and to the sides of steep slopes. You could be on flat ground hundreds or thousands of feet below an avalanche starting zone and still trigger an avalanche that reaches you and your travel partners.  

  

• 

  Storm Slabs

  N

  NE

  E

  SE

  S

  SW

  W

  NW

  • Alpine
  • Treeline
  • Below treeline

  Likelihood

  Very Likely

  Size

  1.5–2.5

  What and where is it?  You could trigger 1-4 foot thick slabs on all aspects at middle and upper elevations. Slabs will be thicker as you gain elevation and / or enter terrain exposed to the wind. 

  How can you recognize it?  Due to the impressive snowfall amounts and warm temperatures, the slabs exist on most slopes over about 8000' and on some slopes below that. Expect to find thicker, denser slabs below exposed ridgelines and cornices, on the sides of cross-loaded gullies, and on aprons and slopes below large chutes and cliff faces. 

  How can you manage it?  The easy answer is "stay off of, away from, and out from beneath all steep slopes." In wind-sheltered areas, you're more likely to trigger slides as the slope angle increases from 30*. Some slides involving the "new snow" could behave like Persistent Slab avalanches: they break wider and higher on the slope than expected.